1. Field of the Invention
The invention relates to a torsional vibration damper for the drive line of a motor vehicle of the type including an input damper part that is rotatable about an axis of rotation, an output damper part that is rotatable about the axis of rotation in relation to the input damper part over a limited relative angle of rotation, at least one spring device coupling the two damper parts together in a rotationally elastic manner, and at least one friction device effective between the two damper parts and having a friction ring axially clamped between two friction surfaces by axial spring force.
2. The Prior Art
A clutch disk with a torsional vibration damper of the foregoing type is disclosed in German Patent No. 23 23 872. As there disclosed, a first friction device is arranged axially between a side flange and the disk forming the input damper part of the torsional vibration damper and includes friction rings made of frictional or bearing materials. A second friction device, which is coupled with a side flange so as to have play in rotation, includes a supplementary friction ring, on both axial sides of which are arranged linings made of frictional or sliding material. Friction rings consisting entirely of frictional material are prepared from reinforced synthetic plastic, for example, in such a way that a synthetic plastic, especially polyamide to which glass fiber particles are admixed, is injection-molded to form ring disks. Such friction rings are, per se, stable and storable, but have the drawback that during operation the glass fiber particles may reach the frictional surfaces. The consequence of this is an increased material wear of the opposite friction surfaces and an uncontrollable increase of the force of friction. If the friction ring is prepared from polyamide devoid of reinforcing materials, then a constant frictional behavior of the friction ring can be achieved over its entire service life. In that case, however, the friction ring has an insufficient structural strength.